Electric discharge tube



Dec. 11, 1934. p w DOBBEN 1,983,743

ELECTRIC DISCHARGE TUBE Filed March 22, 1929 Patented Dec. 11, 1934 UNITED STATES PATENT OFFICE lands, usignor, by meme assignments,

toladio Corporation of America, New York, N. Y a corporation of Delaware Application March 22, 1929, Serial No. 349,149 r m the Netherlands April 19, ms

4Claims.

The invention relates to gas fllled electric discharge tubes.

Electrodes in gas filled electric discharge tubes, for example in rectiflers, are subject to volatilization or disintegration due to the collision of elec- ,trically charged particles. Current supply wires and other metal parts located in the neighborhood of the discharge path may also be exposed to a bombardment by these particles unless they are protected therefrom by some means. Such a protecting means has been suggested by the applicant in the prior application No. 272,390, filed April 24, 1928, according to which disintegration of metal parts which do not act as electrodes, is avoided by coating these parts with an insulating layer consisting of enamel. Another known method of protecting supplyv wires consists in surrounding them by small glass tubes. When enamel is used as protecting means, it may occur under definite conditions, for example when the conducting parts of the tube are being deprived to the utmost degree of occluded gases, that due to the intense heating of the electrodes the enamel melts and flows away so that the protection is eliminated at the point at which it is most needed. If supply wires are surrounded by loose tubes, it is nevertheless possible that at the ends thereof undesirable discharges are produced which give rise to the destruction of the material to be protected and of that of the small tubes, if used.

In an electric discharge tube according to the invention, one or more conducting parts are cov- -ered with a baked ceramic mass of high melt'-- ing point. This mass may be baked on to metal parts of the tube. According to the invention, insulating parts adjacent to conducting parts of the tube may also be coated with the same mass. In one particular mode of realization of a discharge tube according to the invention, the baked ceramic mass is sealed to glass parts of the tube. Thus, for example, supply wires of such a tube may be surrounded by small glass tubes which at one end are sealed to the stem or pinch whereas the other end is sealed to a small tube of a baked ceramic mass of high melting point. The mass utilized in accordance with the invention, preferably consists either entirely or partly of a mixture of kaolin and borax. Porcelain or steatite 'may also be advantageously used.

The invention will be more clearly understood by referring to the accompanying drawing in which Figure 1 represents an electrode for a multiphase rectifier according to the invention.

Figure 2 shows a two-phase rectifier comprising an incandescent cathode and Figure 3 represents a stem of a two-phase rectifler whose construction is somewhat diiferent from that of the preceding figure.

Referring to Figure 1, an electrode 2 which, for example, consists of carbon, is mounted inside a glass envelope 1 and is carried by a supply wire indicated by' a dotted line 3. This supp y wire is surrounded by a small tube 4 of insulating material which serves to protect the wire from disintegration. It has been stated that nevertheless it is still possible that undesirable discharges are produced at the point at which the said tube terminates in the electrode 2. According to the invention, this is avoided by means of a baked ceramic mass 6 of high melting-point which is applied to the lower side of the electrode so as to surround the tube 4, the narrow opening between the tube 4 and the wall of the cavity 5 of the electrode being thus sealed owing to which even at the point at which the disintegration would be strongest the material of the supply wire remains perfectLv intact.

The tube represented in Fig. 2 comprises two anodes 12 and 13 and an incandescent cathode 14 which are all mounted within an envelope 11 on the press 15 of the foot or stem 16 of the tube. The supply wires are each coated with a layer 17, 18' of ceramic mass of high melting-point which is baked on to the said wires. On the press are sealed short glass tubes 19 and 20 which surround the coated supply wires.

when following the method as shown in Figure 3one obtains a seal which is still more perfect. In fact with a tube as represented in Fig. 2, there may'still be produced a discharge passing through the space left between the glass tubes and the insulation of the wire. In the construction as shown in Fig. 3 this is prevented by small tubes 21 and 22 of baked ceramic mass, for example pipe-clay, which are sealed to the edge of the protruding 8 888 cylinders 23 and 24, a discharge being thus rendered impossible at these points. At the upper end of the tubes the protectionis obtained according to the method shown in Figure 1, namely by means of a covering of ceramic mass of high melting point as indicated at 25 and 26. In this case the supply wires are consequently entirely enclosed so that disintegration is prevented and the production of discharges to other surfaces than that of the electrodes is rendered impossible. The supply wires of the incandescent cathode may without any objection be coated with enamel because in this case there is but little possibility of the enamel being heated during the deprivation of occluded gases to such an extent that it melts. According to the invention, however, these wires as well as other parts of the tube which do not act as electrodes such for example as shields or supports may be coated if desired with the above mentioned mass.

What I claim is:

1. A gas filled electric discharge tube comprising a plurality of electrodes, supply wires therefor, a short glass tube surrounding each of said supply wires and sealed to the stem of the tube, and a ceramic mass of high melting point surrounding and in intimate contact with at least one of the said' supply wires, the said mass being at one end sealed to the said glass tube, and

a second ceramic mass of high melting point baked on the supply wire at the other end, said two ceramic masses being sealed to each other for preventing the passage of bombarding particles to the joints protected by the ceramic masses.

2. A gas filled electric discharge tube comprising a cathode and at least one anode, a supply wire for said anode, an'insulating member surrounding the supply wire, and a ceramic mass of high melting point baked in position, intimately contacting with the said anode supply wire, and connected by a baked seal at one end to said insulating member and at the other end to the rear of the anode, whereby the passage of bombarding particles to the seals between the supply wire and the insulating material and anode is prevented;

3. A gas filled electric discharge tube comprising a cathode and at least one anode, a. supply wire for said anode, an insulating tube of ceramic material surrounding said supply wire, said tube being sealed at one end to a part of the stem of the tube, and a ceramic mass, baked in position, in intimate contact with the rear side of said anode and at its other side in intimate contact with said insulating tube.

4. An electric discharge tube comprising a reentrant stem, a lead-in conductor having one end sealed within the stem, an electrode carried at the other end of said conductor, an insulating tube of ceramic material surrounding said conductor, one end of said tube also being sealed within the stem, and a ceramic mass of high melting-point baked onto the other end of said insulating tube and in intimate contact with a portion of the electrode.

PIETER WILHELM DOBBEN. 

